Brake disc structure

ABSTRACT

An annular brake disc having an annular braking member on which at least one radially-extending face is furnished with a friction facing which is provided by a series of segmental-shaped friction pads that are secured to the braking member. Each friction pad is constructed of a soft or brittle material such as carbon and has at least one substantially straight edge. In order to transmit braking loads, this edge is chamfered so as to fit into a corresponding inclined undercut abutment face in the member, of which the following is a specification.

United States Patent [1 1 Doweli et a1.

[451 Sept. 18,1973

[ BRAKE DISC STRUCTURE [75] Inventors: Frederick S. Dowell; Benedict P.

Healy, both of Coventry, Warwickshire, England [73] Assignee: DunlopLimited, London and Birmingham, England [22] Filed: Mar. 1, 1972 [21]Appl. No.: 230,632

[30] Foreign Application Priority Data Mar. 2, 1971 Great Britain5,738/71 [52] US. Cl. 188/218 XL, 188/73.2, 188/251 A, 192/70.13,192/107R [51] Int. Cl. F168 65/12 [58] Field of Search 188/73.2, 218 XL,188/251 A, 250 G, 234; 192/107 R, 107 M, 70.13

[56] References Cited UNITED STATES PATENTS Davis 188/218 XL 7/1969Lattemant 188/218 XL 1,796,433 3/1931 Blume 188/234 X 2,059,576 11/1936Glick i 192/107 R 3,552,533 l/l971 Nitz 188/251 A X 3,605,967 9/1971Warren et al l88/73.2 X

Primary Examiner-George E. A. Halvosa Attorney-John A. Young 57]ABSTRACT 10 Claims, 15 Drawing Figures Patented Sept. 18, 1973 3,759,354

7 Sheets-Sheet l Patented Sept. 18, 1973 7 SheetsSheet 2 SECTION A-AFIG. 2.

SECTION 5-8 FIG.4.

Patented Sept. 18,1973 I I 3,159,354

7 Sheets-Sheet 5 SECTION D-D F|G.7.

Patented Sept. 18, 1973 3,759,354

'7 Sheets-Sheet 4 Patented Sept. 18, 1973 7 Sheets-Sheet 5 PatentedSept. 18,1973 3,759,354

7 Sheets-Sheet 6 FIG. n.

Patented Sept. 18, 1973 3,759,354

'7 Sheets-Sheet 7 BRAKE DISC STRUCTURE This invention relates to brakesand more particularly to friction members for brakes.

Materials used in brake friction elements may have relatively weakstructural properties, and problems arise in attaching such elements tothe relatively strong supporting members which have to be provided toenable braking loads to be transmitted. This problem is particularlyacute in aricraft brakes, where very high temperature, pressure andtorque loads are encountered, and this tends to restrict the choice offriction materials available to the designer. One material which isparticularly difficult to secure satisfactorily to a braking member iscarbon, which on account of its high frictional and heat capacityproperties together with its low density is otherwise a particularlyattractive material for use in an aircraft brake.

One object of the present invention is to provide a brake mamber,suitable for use as a rotor or stator member in an aircraft brake;incorporating friction pads of carbon or other soft or brittle materialand in which the pads are securely fixed to a backing member. Accordingto the invention an annular brake disc comprises an annular backingmember having at least one radially-extending face furnished with afriction facing provided by a series of segmental-shaped friction padssecured to the backing member, the friction elements each being of softor brittle material such as carbon and each having at least onesubstantially straight edge which is chamfered so as to fit into andtransmit braking torque loads to a correspondingly inclined undercutabutment face associated with the backing member.

Preferably, both edges of each of the pads are chamfered so as to fitinto corresponding undercut faces on the backing member, the pads beingheld by the abutments against circumferential movement in eitherdirection.

Various embodiments of the invention will now be described, by way ofexample with reference to the accompanying drawings in which:

FIG. 1 is a view of part of the brake disc assembly as seen in adirection parallel to the axis of rotation of the disc;

FIG. 2 is a sectional view on the line A-A of FIG. 1 showing theassembly of the friction pads on the brake member;

FIG. 3 is a view similar to FIG. 1 showing a second embodiment of theinvention;

FIG. 4 is a sectional view on the line 8-8 of FIG. 3;

FIG. 5 is a view similar to FIGS. 1 and 3 showing a third embodiment ofthe invention;

FIG. 6 is a sectional view on the line C-C of FIG. 5; FIG. 7 is asectional view on the line D-D of FIG.

FIG. 8 is a view similar to FIGS. 1, 3 and 5 showing a fourth embodimentof the invention;

FIG. 9 is a sectional view along the line EE of FIG.

FIG. 10 is a view similar to that of FIG. 9 showing a fifth embodimentof the invention;

FIG. 11 is a view similar to that of FIG. 9 showing a sixth embodimentof the invention;

FIG. 12 is a view of part of a brake disc assembly as seen in adirection parallel to the axis of rotation of the disc showing a seventhembodiment of the invention;

FIG. 13 is a sectional view on the line F-F of FIG. 12 showing theassembly of the friction pads on the brake member;

FIG. 14 is a view similar to FIG. 12 showing an eighth embodiment of theinvention, and

FIG. 15 is a sectional view on the line G-G of FIG. 14.

In a first embodiment, shown in FIG. 1, a rotor 1 for an aircraft brakeof the multi-disc type comprises an annular backing member 2 in the formof a steel disc having radially projecting drive dogs on its outercircumference. The disc 2 is machined on each face so as to providerecesses 4 of segmental shape into which carbon friction pads 6 are tobe secured. The recesses, of which there may be 10 on each face, arebounded by integrally formed radially-extending abutment strips (FIG. 2)which are undercut at each side to form inclined abutment faces 5 intowhich correspondingly chamfered edges of the adjacent friction pads 6are arranged to fit in dove-tail fashion.

The arrangement is such that each pad is located against circumferentialmovement in either direction by the wedging engagement of theappropriate chamfered edge of the pad 6 into the associated abutmentface 5. This subjects the friction pad almost entirely to compressionstresses in the abutment zone, and these stresses can be resisted by therelatively soft material of the friction pad very much more easily thantensile or shear stresses.

Each friction pad is located against radially inward movement by theradial wedging action as it moves inwardly between the two associatedabutments, and is prevented from moving outwardly by small metal keepplates 3 rivetted onto the drive dogs.

The backing member 2 may alternatively be of a Nickel based refractoryalloy or molydenum to withstand higher temperatures, or may be ofBeryllium. Where a Beryllium backing member is used it may be preferableto use relatively thin pads with a relatively thick backing member so asto utilise the high heat capacity of the Beryllium. In otherconstructions the carbon pads 6 would normally be thick relative to thethickness of the backing member and would provide the major contributionto the heat capacity of the brake member. The backing member may also beconstructed of carbon with carbon fibre reinforcement.

In a second embodiment, shown in FIGS. 3 and 4, the backing member 10 isnot machined to provide the recesses for the friction pads, instead theundercut abutment faces 12 are constituted by suitably shaped channelsection strips 11 of metal rivetted or welded to the backing member.

In a third embodiment shown in FIGS. 5, 6 and 7, the radially-extendingthermal relief slots 14 which are commonly provided in a brake disc areemployed to provide locating means for a pre-formed abutment strip 15.The abutment strip 15 is of I-I-shaped cross-section so as to fit intothe thermal relief slot 14 and carries inclined abutment surfaces 16 onthe two portions which project on each side of the disc 19. Since thethermal relief slot does not extend through the whole radial width ofthe brake disc, the central portion of the H- section strip at one endis machined away so that the two separate limbs thus formed can embracethe nonslotted portion of the disc 17, and the strip is secured to thedisc by a rivet 18 through this portion.

In a fourth embodiment shown in FIGS. g and 9, the backing member 29 isformed with a series of apertures 21, for example circular, one for eachpair of friction pads 22 located one on each side of the backing member20. The abutment members may be formed as in any of the examplesdescribed above, and the apertures incorporate plates 23 of heatabsorbing material, which may be the same material as that of thefriction pads, fitted within the apertures.

in a fifth embodiment, shown in FIG. 10, apertures are provided asdescribed with reference to the fourth embodiment, and the opposedfriction pads 25 on each side of the aperture are formed withprojections which each fit within the aperture and meet in the centralplane 26 of the backing member 27 to provide an uninterrupted heat paththrough the brake member. In this example the abutment strips 28 must beof the kind which is secured to the backing member 27 rather than thatwhich is formed integrally therewith, since the pads 25 have to beplaced in position on the backing member 27 before the abutment strips28 are placed in position.

ln a sixth embodiment of the invention shown in FIG. 11, the abutmentstrips 30 are of carbon/carbon fibre reinforced composite materialarranged in such a manner that the carbon fibres extend in a radialdirection relative to the backing member 32. The abutment strips mayalso be constructed of any reinforced composite material having frictionand wear properties compatible with those of the friction pads. Eachabutment strip 30 is of wedge-shaped section and carries inclinedsurfaces 31 on each longitudinal side which abut correspondinglychamfered surfaces of the carbon friction pads 34. The abutment stripsand backing member 32 are provided with a number of axial drillings 33countersunk at each end to take a rivet 37. The rivet 36 attaches anabutment strip 30 to each side of the backing member 33 and therebysecures the friction pads 34 to the member 32. The abutment strips maybe so constructed that the axial outward faces 35 of the friction pads34 are flush with the outward face 36 of the carbon fibre reinforcedabutment strips 30 and serve as part of the friction surface of thebrake. Alternatively the outward faces 36 of the carbon fibre reinforcedabutment strips may be positioned in a plane axially inwardly of theface 35 of the friction pads 34.

Where the brake disc is a stator member, the radially projecting drivedogs are positioned on the inner circumference and therefore in theabsence of drive dogs on the outer circumference of the backing member,the keep plates may be attached directly to the backing member.

Alternatively, in a seventh embodiment, as shown in FIGS. 12 and 1'3,abutment strips (40) are provided with a Y-shaped outwardly flaredportion 41 adjacent the outer circumference of the backing member 42.The friction pads 43 are correspondingly shaped to accommodate thisflared end portion and the combination of the flared abutment strip 40and the pads 43 causes a wedging action which prevents radial outwardmovement of the pads.

In an eighth embodiment of the invention, shown in FIGS. 14 and 15, theabutment member 45 is in the form of a triangular wedge 35 carrying theundercut abutment faces 47 corresponding to the chamfered edges ofadjacent friction pads 48 which are cut away to accommodate the abutmentmember and act to prevent radial outward movement without the need foradditional keep plates. The wedge shaped abutment member is secured byrivets $9 to the backing member 50 preventing radial and circumferentialmovement of the friction pads 48.

In order to provide adequate retention of the friction pads thetriangular abutment member is provided with an included angle betweenits sides 45a and 45b greater than 360/n where n is the number ofabutment members on one side of each backing member. This also appliesto the included angle between sides 40a and 40b of the Y shaped portionof the abutment member as shown in FIG. 12.

The friction members described above have the advantage that the carbonpads are not secured by rivets or screws which would pass through thepad and for which holes would need to be provided in the pad. Such holeswould weaken the pad and would necessitate the provision of areinforcement for the carbon which gives rise to considerable practicaldifficulties.

We claim:

1. An annular brake disc comprising an annular backing member, a numberof circumferentially spaced abutment members secured to the backingmember and arranged to extend radially relative to said backing member,and a series of circumferentially-spaced friction pads of soft orbrittle material such as carbon secured to the backing member by theabutment members, each pad being provided with two substantiallystraight chamfered edges which each respectively cooperate with undercutabutment faces provided on the associated abutment members so as totransmit braking torque loads from the pads to the backing memberwithout failure of the pad material, a portion at least of each abutmentface being arranged to extend at an angle to the mean radius of thebacking member along which the respective abutment member extendswhereby the tendency of the friction pads to move radially outwardlyunder the action of the resultant frictional force acting on the padsduring use is restrained.

2. A brake disc according to claim 1 wherein the backing member isprovided with a separately formed abutment member of reinforcedcomposite material having wear properties compatible with those of thefriction pads.

3. A brake disc according to claim 1 wherein the abutment member isgenerally Y-shaped when viewed in the axial direction of the disc havingan outwardly flared portion adjacent the outer circumference of thebacking member so as to prevent radially outward movement of theassociated pads.

4. A brake disc according to claim l comprising an annular backingmember having radially projecting drive dogs from one circumferentialedge.

5. A brake disc according to claim 1 wherein the backing member isconstructed of a Nickel based refractory alloy.

6. A brake disc according to claim 1 wherein the backing member isconstructed of Molybdenum.

'7. A brake disc according to claim 1 wherein the backing member isconstructed of Beryllium.

8. A brake disc according to claim 1 wherein the backing member isconstructed of carbon reinforced with carbon fibres.

9. A brake disc according to claim 1 wherein the friction pads arelocated in pairs comprising one pad on each side of the backing memberand the portion of the 3,759,354 6 backing member between the pads ofeach pair of fricjection extending within the aperture to contact thetion pads is provided with an aperture incorporating heat absorbinmaterial. v

10. A brake disc according to claim 9 wherein at least heat path throughthe brake disc one of each pair of friction pads is formed with a pro- 5other friction pad so as to provide an uninterrupted

1. An annular brake disc comprising an annular backing member, a numberof circumferentially spaced abutment members secured to the backingmember and arranged to extend radially relative to said backing member,and a series of circumferentially-spaced friction pads of soft orbrittle material such as carbon secured to the backing member by theabutment members, each pad being provided with two substantiallystraight chamfered edges which each respectively co-operate withundercut abutment faces provided on the associated abutment members soas to transmit braking torque loads from the pads to the backing memberwithout failure of the pad material, a portion at least of each abutmentface being arranged to extend at an angle to the mean radius of thebacking member along which the respective abutment member extendswhereby the tendency of the friction pads to move radially outwardlyunder the action of the resultant frictional force acting on the padsduring use is restrained.
 2. A brake disc according to claim 1 whereinthe backing member is provided with a separately formed abutment memberof reinforced composite material having wear properties compatible withthose of the friction pads.
 3. A brake disc according to claim 1 whereinthe abutment member is generally Y-shaped when viewed in the axialdirection of the disc having an outwardly flared portion adjacent theouter circumference of the backing member so as to prevent radiallyoutward movement of the associated pads.
 4. A brake disc according toclaim 1 comprising an annular backing member having radially projectingdrive dogs from one circumferential edge.
 5. A brake disc according toclaim 1 wherein the backing member is constructed of a Nickel basedrefractory alloy.
 6. A brake disc according to claim 1 wherein thebacking member is constructed of Molybdenum.
 7. A brake disc accordingto claim 1 wherein the backing member is constructed of Beryllium.
 8. Abrake disc according to claim 1 wherein the backing member isconstructed of carbon reinforced with carbon fibres.
 9. A brake discaccording to claim 1 wherein the friction pads are located in pairscomprising one pad on each side of the backing member and the portion ofthe backing member between the pads of each pair of friction pads isprovided with an aperture incorporating heat absorbing material.
 10. Abrake disc according to claim 9 wherein at least one of each pair offriction pads is formed with a projection extending within the apertureto contact the other friction pad so as to provide an uninterrupted heatpath through the brake disc.